In general, heat transferring or transmitting apparatus of the character described utilizing phase transition comprises a condensor disposed above an evaporator and connected thereto by a conduit, with a suitable amount of a condensable coolant being sealed in the system of the evaporator, the condensor and the conduit. The coolant in its liquid form is vaporized by the latent heat of gasification in the evaporator and is fed to the condensor by the increasing pressure caused by the gasification and the coolant gas is then condensed by discharging its latent heat, whereupon the condensed coolant liquid flows downward into the evaporator under the force of gravity, and thus the circulation of the coolant is achieved. Accordingly, it is unnecessary to provide a circulation pump, whereby the apparatus can be of simple construction and a large quantity of heat can be effectively transferred or transmitted with a small difference of temperature when the phase transition of a coolant is so utilized.
An important part or element can thus be electrically insulated by using an electrical insulation coolant, whereby the system described is especially suitable for cooling electrical apparatus, and especially, for example, a large capacity semiconductor device which requires high efficiency of heat transfer and the radiation of heat out of the apparatus.
FIG. 1 of the Drawings shows one embodiment of a conventional apparatus which is applied as a heat transferring apparatus utilizing such phase transition of a coolant for cooling a semiconductor device. In this illustration, the reference numeral 1 designates a stack having the structure of a semiconductor or heat generating device equipped with a radiator, which is disposed in an evaporator 2 having a coolant liquid 3 therein so as to cover the stack 1. A condensor 4 is positioned above the evaporator 2 and is connected thereto by a conduit 5 oriented substantially vertically therebetween. Radiation fins 6 are provided about the exterior wall of the condensor 4 for effectively radiating the heat out of the apparatus. Sealed terminals 7 are provided in the evaporator walls for electrically connecting the stack 1 to a suitable power source.
In the conventional apparatus, the coolant 3, which is vaporized by absorbing heat being generated from the stack 1 in the evaporator 2, is fed upward through the conduit 5 to the condensor 4, as shown by the dotted arrow line 8, in a rapid manner by the increasing pressure caused by the gasification in the evaporator and the heat is then discharged by the contacting of the coolant gas with the wall of the condensor, so as to transition the coolant to a liquid phase. On the other hand, the condensed coolant liquid is then returned by flowing down along the inside of the wall of the conduit 5 to the evaporator 2, as shown by the full arrow line 9, where it is used again for cooling the stack 1. The vaporization and the condensation steps are repeated continuously and simultaneously by maintaining the thermal transferring function by phase transition.
However, the natural circulation of the coolant can be smoothly performed only when the quantity of heat is relatively small. Such natural circulation cannot be smoothly performed when the quantity of heat being transferred is substantially increased. This is because the coolant gas and the coolant liquid are counter-currently passed through the conduit 5, as shown by the arrow lines 8 and 9, and accordingly, when the velocity of the coolant gas rising in the conduit 5 increases, depending upon an increase of the heat being transferred, the downward flowing coolant liquid is essentially pushed back thereby toward the condensor side by the friction occurring between the coolant liquid and the coolant gas.
Moreover, the coolant liquid is thus clogged in the conduit 5 so as to disturb the passing of the coolant gas by the coolant liquid, wherein a partial heat-exchange occurs therebetween in the conduit, so as to prevent the proper flow down of the coolant liquid, and at last to defeat completely the function of the heat transferring apparatus. Such trouble is easily caused, depending upon a longer conduit or a curve, a step or a dead end in the conduit, whereby the efficiency of heat transfer becomes unstable and enough heat transfer function cannot be imparted when a large quantity of heat is to be transferred. Thus, in the conventional apparatus, in order to overcome the trouble, the condensor is brought as close to the evaporator as possible, and they are connected by a linear and thick conduit. However, the application or construction is thus limited, disadvantageously.
As stated above, the heat transferring apparatus utilizing natural circulation and phase transition of a coolant has various advantages, however, such troubles as discussed have caused the prevention of the practicl application thereof.